Apparatus for spreading filaments

ABSTRACT

Apparatus and process are provided for spreading continuous filaments entrained in a stream of air flowing from a high velocity air gun. The filaments are spread in a separator having a generally round inlet in communication with the outlet of the air gun which progressively changes in shape to a generally slot shaped outlet equal to or up to 10 times larger in size than the inlet, the longer sides of the slot being from 2 to 300 times greater in length than the shorter sides of the slot. To obtain further spreading of the filaments, generally parallel laterally extending spreaders are positioned adjacent the ends of the outlet slot of the separator and at right angles thereto.

9 United States Patent 1191 1111 3,7135% Dorschner et al. 1 1 Jan. 30, 1973 54 APPARATUS FOR SPREADING 3,467,316 9 1069 Hancock ..239 597 x FILAMENTS 3,047,203 7/1962 Coanda .239 010. 1 3,227,157 1/1966 Courtin ..239/597 X [75] Inventors: Oskar Dorschner, Bad Homburg;

Christoph Storkebaum, Egelsbach; FOREIGN PATENTS OR APPLICATIONS f zig f l fi g $35 2: l,l38,640 10 1962 Germany ..239 419.5 Germany Primary Examiner-M. Henson Wood, Jr. [73] Assignee: Metallgesellschait Aktiengesellschait, Assistant Examiner-Thomas C. Culp, Jr. Frankfurt am Main, Germany Attorney-Burgess, Dinklage and Sprung [22] Filed: July 16, 1970 [57] ABSTRACT [21] Appl' 55327 Apparatus and process are provided for spreading continuous filaments entrained in a stream of air flow- [30] Foreign Application Priority Data ing from a high velocity air gun. The filaments are spread in a separator having a generally round inlet in July l7, 1969 Germany ..P I9 36 3543 communication with the outlet of the air g which [52] U S Cl 239/597 239/419 5 progressively changes in shape to a generally slot [51] B05b 6 shaped outlet equal to or up to I0 times larger in size [58] Fie'ld 7 509 than the inlet, the longer sides of the slot being from 2 5 5 6 to 300 times greater in length than the shorter sides of the slot. To obtain further spreading of the filaments, generally parallel laterally extending spreaders are [56] References cued positioned adjacent the ends of the outlet slot of the UNITED STATES PATENTS separator and at right angles thereto. 2,794,683 6/1957 Michaels ..239/597 X 8 Claims, 15 Drawing Figures APPARATUS FOR SPREADING FILAMENTS BACKGROUND 1. FIELD OF THE INVENTION This invention relates to a process and apparatus for depositing continuous filaments drawn at high velocity by an air gun to form a non-woven product. More particularly, this invention relates to process and apparatus for aerodynamically spreading filaments prior to their being deposited.

ln copending application Ser. No. 865,128, filed Oct. 9, 1969, which is a continuation-in-part of copending applications Ser. No. 693,017, filed Dec. 22, 1967, now abandoned and Ser. No. 783,556, filed Dec. 13, 1968, now abandoned and assigned to the same assignee as this application, a non-woven web is formed by simultaneously spinning a multiple number of continuous filaments of a synthetic polymer. The spinning is effected in the conventional manner from the melt, with for example the melt of the polymer being extruded through a multiple number of downwardly directed spinning nozzles or spinnerets preferably extending in a row or multiple number of rows. The filaments as they are spun are gathered into a straight row of side-byside, evenly spaced apart, untwisted bundles each containing at least 15 and preferably from 50 to 150 filaments. These filament bundles are simultaneously drawn downwardly at a velocity of at least 3,000 meters per minute, and preferably from 3,500 to 8,000 meters per minute in individually surrounding gas columns Flowing at a supersonic velocity and thus directed to impinge on a substantially horizontal carrier. The gathering of the filaments into the bundles and their drawing and directing to impinge on the carrier is preferably effected by passing the bundles through air guns which surround the filaments with a column or jet of air which is directed downward at supersonic velocity. The air guns are arranged so as to extend in a straight row in a direction extending across the carrier at right angles to its direction of movement, so that the bundles confined in the gas columns as the same strike the moving carrier extend in a line or row at right angles across the carrier. The carrier may be a conventional carrier used in the non-woven art,such as an endless carrier or belt screen or the upper portion of a drum, asfor example a screen drum. The filament bundles containing a number of parallel filaments are laid down on the carrier in a loop-like arrangement with primary loops extending back and forth across the width of a section defined by the impingement of the air column from one air gun on the carrier. Before and as the parallel filament bundles impinge the carrier, they are broken up into sub-bundles containing a lesser number of parallel filaments and forming secondary small loops and swirls which overlap each other and those of adjacent sections to result in substantially complete intermingling with the overlapping portions of adjacent sections. The laid-down filament bundles then form a continuous uniform non-woven web which may be consolidated and stabilized by compacting, heat-sealing, needling or treating with a binder, e.g., latex and other further treatments known in the art.

And in copending application Ser. No. 850,500, filed Aug. 15, 1969, also assigned to the same assignee of this application there is disclosed a high velocity air gun or aspirator jet having a nozzle and a throat for drawing-off thermoplastic filaments as in the process of copending application Ser. No. 865,128, discussed above. The primary aspirating air is smoothly expanded to supersonic velocities through a throat into an out- 5 wardly diverging expansion chamber which is preferably dome-shaped. A guide tube for the filaments and secondary air extends centrally through the throat and through the expansion chamber to the draw-off tube, which has a constant diameter. The design is such that the aspirating air flows parallel to the filaments issuing from the guide tube and does not impinge thereon as is the case with the jet designs of the prior art.

2. PRIOR ART In the production of non-woven materials from continuous filaments, the prior art has proposed several devices and processes for preventing or minimizing bunching, clustering, roping, tangling, and intermingling of groups of continuous filaments as they are drawn down and deposited, none of which have been proven to be entirely satisfactory. This problem is a serious one because bunching, roping and the like of the filaments results in a non-uniform and irregular non-woven product.

One approach has been to limit the number of filaments drawn by each air gun to 2 to 25, for example. However, this seriously reduces the efficiency of the drawing process since the air guns are normally capable of drawing a much higher number of filaments. On top of this,.a larger number of air guns must be used to form a non-woven product which makes the process more costly.

Another approach has been to electrostatically charge the filaments so that they repel each other and spread apart as they emerge from the air gun. This approach, however, involves expensive apparatus, results in high energy losses and is sensitive to moisture in the atmosphere which can be absorbed by the filaments which reduces the effect of electrostatic charging. Also, this process is limited by the speed at which the filaments can be drawn for adequate electrostatic charging.

Yet another approach is set forth by Franke in US. Pat. No. 3,325,906. Here the boundary layer of air which is created along the side walls of a diffuser is removed by means of a vacuum which causes the filaments to spread. Without the vacuum the diffuser is ineffective for spreading a strand of filaments.

SUMMARY The shortcomings of the prior art are overcome according to the present invention whereby bunching, clustering, roping, tangling and intermingling of groups of continuous filaments are prevented and the filaments are spread aerodynamically prior to depositing resulting in a uniform, regular, non-woven product.

According to the present invention continuous filaments entrained in a stream of air flowing from a high velocity air gun are spread in an apparatus comprising a separator having a generally round inlet in communication with the outlet of the air gun which progressively changes in shape to a generally slot shaped outlet equal to or up to times larger in size than the inlet, the longer sides of the slot being from 2 to 300 times greater in length than the shorter sides of the slot. To

obtain further spreading of the filaments, laterally extending spreaders are positioned adjacent the ends of the outlet slot of the separator at right angles thereto. These spreaders, in generally parallel alignment, in pairs or successive pairs may also be used in place of the separator.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a separator of the invention shown with preferred spreaders attached.

FIG. 2 is a vertical sectional view taken along line 22 of FIG. 1.

FIG. 3 is a top view of the separator and spreaders of FIG. 1.

FIGS. 4 and 6 are vertical sectional views showing alternate embodiments of the separator of the invention.

FIGS. and 7 are vertical sectional views taken along line 5-5 of FIG. 4, line 7-7 of FIG. 6, respectively.

FIGS. 8, 9, 10 and 11 are perspective views showing alternate embodiments of the spreaders of the invention.

FIG. 12 is a vertical sectional view showing an alternate embodiment of a separator of the invention.

FIG. 13 is a vertical sectional view taken along line 13-13 of FIG. 12.

FIGS. 14 and 15 are vertical sectional views showing alternate embodiments of spreaders of the invention.

DESCRIPTION FIGS. l-3 show a preferred embodiment of this invention which includes a separator 2 attached to the outlet 1 of an air gun (not shown) such as for example the air gun described in copending application Ser. No. 850,500 discussed above. Attached to separator 2 by means of ribs 7 are a pair of generally parallel, laterally extending spreaders 4. Ribs 7 are preferably thin and are positioned to align with the separator 2 as shown in FIGS. 1 and 3. In this manner, ribs 7 present little if any interference with air aspirated between separator 2 and spreaders 4. Other means such as multiple ribs can be employed to attach the spreaders to separator 2 and, if desired, the spreaders 4 can be mounted independently of separator 2 and positioned as shown in FIGS. 1-3.

As shown in FIGS. 1-3, separator 2 has a generally round inlet which in this embodiment is formed by the air gun outlet 1. The phrase generally round is intended to include other configurations such as oval, square and the like which are not inconsistent with the purpose and function of the separator 2. The inlet of separator 2 is generally the same size as the outlet 1 of the air gun but can also be larger. The separator 2 progressively changes in shape from its generally round inlet to a generally slot shaped outlet which is preferably curved as shown in FIG. 1 by reference numeral 10.

The outlet of separator is equal to or up to 10 times larger in size, preferably 3 times larger, than the size of the inlet. The actual area of each opening is taken as the size. In addition, the longer sides of the outlet slot are from 2 to 300, preferably from 5 to 100, times greater in length than the shorter sides of the slot. When the outlet slot is curved as is shown in FIG. 1, the radius of curvature is from 0.1 to 20, preferably 0.2 to 10, times the length of the seperator 2, measured along the central axis thereof from the inlet.

The interior walls 3, referring to FIGS. 1 .and 2, of the separator 2 may be straight or curved (FIGS. 4 and 5) or straight and curved (FIGS. 6 and 7), and can be any combination of the foregoing. The walls 3 should generally be smooth and may take any suitable shape such as those illustrated which is not inconsistent with the purpose and function of the separator.

Referring to FIGS. 5 and 7, the side walls 9 connecting walls 3 may taper towards each other (FIGS. 2 and.

5) or may be parallel over a part or all of their length (FIG. 7).

The configuration and the relative dimensions of the separator of this invention are such that filaments passing therethrough are aerodynamically spread into a fan shaped pattern by the separators of FIGS. 7-7, for example.

Referring to FIGS. l-3 and 8-11, the spreaders 4 of the invention are shown to be generally parallel, laterally extending members which can be positioned adjacent the outlet of the separator 2 at right angles thereto or they can be positioned adjacent the air gun outlet 1 without a separator. The spreaders 5 shown in FIGS. 1 and 8-11 are symmetrical with respect to the vertical axis of the separator. Thus, the spreaders 4 can function to spread filaments from an air gun or further spread filaments from separator 2.

In all instances the spreaders 4 are positioned such that there is an open space through which air can be aspirated by the air entrained filaments flowing therebetween. This space may be between the air gun and spreaders 4 or between separator 2 and spreaders 4 (FIG. 1).

As air entrained filaments flow between spreaders 4, a wall-flow or Coanda effect along interior walls 5 takes place which causes the filaments to spread. To maximize this effect, the upper edges 6 (FIG. 1) are rounded to prevent eddies and to allow for loss-free entry of aspirated air and the lower edges 8 terminate abruptly to provide for a sharp cut-off of the effect. The Coanda effect is a known phenomenon and is described in 11.8. Pat. No. 2,052,869, issued to I-lenri Coanda on Sept. 1,1936.

As shown in FIG. 1, the upper edges 6 preferably extend above the outlet of separator 2. The inner walls 5, beginning at upper edges 6 first converge towards each other and then diverge from a point below the separator 2 (FIGS. 1, 8-10). The walls 8 can also be parallel before divering (FIG. 12). FIG. 8-11 and 14 show some of the many shapes the spreaders 4 can assume.

In FIG. 14, the use of two pairs of spreaders in succession is shown, the second pair being positioned below and spaced apart from the first pair to permit the entry of aspirated air.

FIG. 15 illustrates an alternate embodiment wherein the spreader 4 is annular and is attached to outlet 1 of an air gun by ribs 7. Here air is aspirated through the spreader to produce a bell-shaped pattern of spread filaments.

FIG. 12 and FIG. 13 show an alternate embodiment of separator 2 wherein the inlet of the separator is larger than the outlet 1 of the air gun which extends into the separator 2 creating an annular space through which air is aspirated into the separator 2.

It is also within the scope of this invention to swing or reciprocate the separator and/or spreaders by known means to increase and/or vary the lay-down pattern of the spread filaments.

While the term air has been used herein in describing the invention, it should be understood that any fluid, heated, cooled or at room temperature may be used in the drawing gun in practicing this invention. Such fluids include steam, water, nitrogen and the like.

The polymeric fibers that may be suitably used in the present invention are oriented crystalline or crystallizable fibers made of any thermoplastic polymer capable of forming a melt which can be spun. Illustrative polymers are the polyolefins, e.g., linear polyethylene, isotactic polypropylene, polyisobutylene, polybutadiene, and the like; polyurethanes; polyvinyls; and the like; polyamides such as polyhexamethylene adipamide and polycaproamide; polyesters such as polyethylene terephthalate and copolyesters of ethylene glycol with a mixture of terephthalic and isoterephthalic acids; or mixed polymers, copolymers, including condensation copolymers, block graft copolymers, and the like, based on the same monomers as the polymers mentioned above. What is claimed is:

1. Apparatus for spreading continuous filaments entrained in a stream of air flowing from a high velocity air gun which comprises a separator having a generally round inlet in communication with the outlet of said air gun which progressively changes in shape to a generally slot shaped outlet and at least two laterally extending spreaders positioned adjacent the ends of said outlet slot at right angles thereto having interior walls along which a wall-flow effect takes place causing said filaments to spread.

2. Apparatus of claim 1 wherein said spreaders are symmetrical with respect to the vertical axis of said separator.

3. Apparatus of claim 1 wherein the upper edges of said spreaders adjacent said outlet are rounded.

4. Apparatus of claim 1 where the lower edges of said spreaders terminate abruptly.

5. Apparatus of claim 1 wherein the interior walls of the spreaders converge from their upper edges and then diverge from a point below said separator.

6. Apparatus of claim 1 which includes a second pair of said spreaders positioned below and spaced apart from said first pair.

7. Apparatus of claim 1 for spreading continuous filaments in a bell-shaped pattern wherein said spreader is annular.

8. Apparatus of claim 1 wherein said outlet is curved and has a radius of curvature of from 0.1 to 20 times the length of the separator measured along the central axis of the separator from said inlet. 

1. Apparatus for spreading continuous filaments entrained in a stream of air flowing from a high velocity air gun which comprises a separator having a generally round iNlet in communication with the outlet of said air gun which progressively changes in shape to a generally slot shaped outlet and at least two laterally extending spreaders positioned adjacent the ends of said outlet slot at right angles thereto having interior walls along which a wall-flow effect takes place causing said filaments to spread.
 2. Apparatus of claim 1 wherein said spreaders are symmetrical with respect to the vertical axis of said separator.
 3. Apparatus of claim 1 wherein the upper edges of said spreaders adjacent said outlet are rounded.
 4. Apparatus of claim 1 where the lower edges of said spreaders terminate abruptly.
 5. Apparatus of claim 1 wherein the interior walls of the spreaders converge from their upper edges and then diverge from a point below said separator.
 6. Apparatus of claim 1 which includes a second pair of said spreaders positioned below and spaced apart from said first pair.
 7. Apparatus of claim 1 for spreading continuous filaments in a bell-shaped pattern wherein said spreader is annular. 